1. Field of the Invention
This invention relates to audio control systems and more particularly to a circuit for mixing a direct audio signal with a reverberation signal component thereof.
2. The Prior Art
In audio control systems such as, for example, amplifier systems utilized with musical instruments, a reverberation effect is frequently provided. This effect is achieved by mixing the direct audio signal with a delayed component of the signal. Normally, there is an undesirable volume increase in the output sound from the system as reverberation signal is added. A more aesthetically pleasing sound is obtained if the volume of the direct signal decreases as the volume of the reverberation signal increases so as to maintain a substantially uniform output volume. The volume of the direct signal may, for example, be reduced by up to 50% when the system controls are set for full reverberation signal.
Heretofore, the only way that the effect indicated above could be obtained was to apply the direct and reverberation signals to opposite ends of a potentiometer, the tap on the potentiometer serving as a volume control for the reverberation signal. A major disadvantage of this type of reverberation mixer circuit is that the potentiometer must have a fairly large resistance to substantially cut off the reverberation signal when the potentiometer is set for zero reverberation. However, with a large-resistance potentiometer, there is significant insertion loss for both the direct and reverberation signals. A need therefore exists for an improved reverberation mixer circuit which permits the desired effect of reducing the amplitude of the direct signal as the amplitude of the reverberation signal is increased without causing a significant insertion loss for either of the signals.